Electrical phase balanced duplexer

ABSTRACT

Embodiments disclosed herein relate to reducing or substantially eliminating an insertion loss caused by isolating a transmit circuit from a receive circuit of an electronic device. To do so, an isolation circuit may be disposed between the transmit circuit and the receive circuit. The isolation circuit may have a first signal path and a second signal path. A first portion of the signal may propagate along the first signal path and a second portion of the signal may propagate along the second signal path. A phase shifter may be disposed on the first signal path to shift a phase of the first portion to match a phase of the second portion. The phase-shifted first portion may be combined with the second portion to reduce or substantially eliminate an insertion loss caused by the isolation circuit.

BACKGROUND

The present disclosure relates generally to wireless communicationsystems and more specifically to isolating wireless signals betweentransmitters and receivers in wireless communication devices.

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present disclosure,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentdisclosure. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

In an electronic device, a transmitter and a receiver may each becoupled to an antenna to enable the electronic device to both transmitand receive wireless signals. Certain electronic devices may includeisolation circuity having an electrical balanced duplexer (EBD) thatisolates the transmitter from received signals, and the receiver fromtransmission signals, thus reducing interference when communicating. Insuch electronic devices, an impedance tuner may be used to match theimpedance of the antenna to increase effectiveness of this isolation.However, the transmission path for transmission signals sent from thetransmitter may branch between the antenna and the impedance tuner. As aresult, some of the power used to transmit a transmission signal throughthe antenna may be lost when the transmission signal branches to theimpedance tuner. Similarly, the reception path for received signalsreceived from the antenna may branch between the receiver and theimpedance tuner. As a result, some of the power in the received signalreceived at the receiver may be lost (e.g., insertion loss) when thereceived signal branches to the impedance tuner.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. Itshould be understood that these aspects are presented merely to providethe reader with a brief summary of these certain embodiments and thatthese aspects are not intended to limit the scope of this disclosure.Indeed, this disclosure may encompass a variety of aspects that may notbe set forth below.

When using an electrical balanced duplexer (EBD) and impedance tuner, itmay be desirable to reduce or recoup the lost power caused by thetransmission path or the reception path branching to the impedance tuner(e.g., referred to as “insertion loss”). Embodiments herein providevarious apparatuses and techniques to reduce insertion loss whilemaintaining isolation of the transmitter and receiver of an electronicdevice. To do so, the embodiments disclosed herein include two circuitpaths between an antenna and an isolation circuit. The isolation circuitis disposed between and coupled to a transmitter circuit and a receivercircuit, and isolates the transmitter circuit from received signals andisolates the receiver circuit from transmission signals. The two circuitpaths may be combined, such that the power divided between the two pathsmay be combined together, thus reducing insertion loss by recoveringpower that may have been lost due to the circuit paths branching (e.g.,from the antenna or the isolation circuit).

In some embodiments, the isolation circuit may include a balun (e.g., atransformer balun) that enables signals (e.g., transmission signals) ofa first frequency range to pass through to the transmitter circuit(e.g., via a transformer effect) and blocks signals of a secondfrequency range from passing through to the receiver circuit, whileenabling signals (e.g., received signals) of the second frequency rangeto pass through to the receiver circuit (e.g., via circuit paths) andblocks signals of the second frequency range from passing through to thetransmitter circuit. In particular, the balun may receive an inputsignal (e.g., traveling in a first direction) and output two outputsignals of opposite polarities (e.g., being 180 degrees out of phasefrom one another), each having half the power of the input signal. Forexample, the balun may receive a transmission signal from thetransmitter circuitry, and output a first split transmission signal anda second split transmission signal, where the first and second splittransmission signals are out of phase with one another by 180 degreesand each have half the power of the original transmission signal.Previously, the first split transmission signal may have been sent tothe antenna for transmission, while the second split transmission signalmay have traveled to an impedance tuner, where the power from the secondsplit transmission signal may have been lost (e.g., resulting ininsertion loss). Instead, the disclosed embodiments may use at least onephase shifter disposed on at least one of the two circuit paths to phaseshift at least one of the split transmission signals so that the twosplit transmission signals are in phase (e.g., have a zero degreedifference in phase).

The balun may also receive two input signals (e.g., traveling indirections different from the first direction) and output a combinedoutput signal. For example, the antenna of the electronic device mayreceive a received signal from the antenna, and split the signal intotwo halves along the two circuit paths. In cases where splitting thereceived signal does not cause a phase difference between the two splitreceived signals, the at least one phase shifter may be deactivated sothat the split received signals may retain their zero phase difference.The balun may receive the two split received signals and combine them tooutput a combined received signal, thus recovering the power that mayhave been previously split off to an impedance tuner. In this way, theembodiments disclosed herein may reduce the insertion loss introduced bythe isolation circuit and therefore improve efficiency of operating anEBD.

In one embodiment, an electronic device is presented which includes anenclosure and one or more processors disposed within the enclosure. Theelectronic device also includes one or more memory devices disposedwithin the enclosure and coupled to the one or more processors, the oneor more memory devices storing instructions, which, when executed by theone or more processors, cause the one or more processors to performvarious operations. The electronic device also includes a displaydisposed at least partially within the enclosure and coupled to the oneor more processors. The electronic device also includes one or moreantennas disposed within the enclosure. The electronic device alsoincludes transmitter circuitry disposed within the enclosure andconfigured to transmit a transmission signal to the one or more antennasvia the isolation circuitry. The electronic device also includesreceiver circuitry disposed within the enclosure and configured toreceive a receive signal. The electronic device also includes isolationcircuitry configured to couple to the one or more antennas via a firstsignal path and a second signal path, and coupled to the transmittercircuitry and the receiver circuitry and configured to isolate thetransmitter circuitry from the receive signal received by the one ormore antennas and isolates the receiver circuitry from the transmissionsignal. The electronic device also includes at least one phase shifterdisposed on at least one of the first signal path and the second signalpath and configured to shift a phase of at least a portion of thetransmission signal therethrough.

In another embodiment, a radio frequency transceiver is presented whichincludes a transmit circuit configured to transmit a transmissionsignal. The radio frequency transceiver also includes a receive circuitconfigured to receive a receive signal. The radio frequency transceiveralso includes an isolation circuit configured to couple to one or moreantennas, the transmit circuit and the receive circuit, the isolationcircuit configured to isolate the transmit circuit from the receivesignal and to isolate the receive circuit from the transmission signal,the isolation circuit coupled to the one or more antennas via a firstsignal path, the isolation circuit configured to couple to the one ormore antennas via a second signal path. The radio frequency transceiveralso includes at least one phase shifter disposed on at least one of thefirst signal path and the second signal path, the at least one phaseshifter configured to shift a phase of at least a portion of thetransmission signal therethrough.

In yet another embodiment, an electronic device is presented whichincludes means for transmitting a transmission signal. The electronicdevice also includes means for receiving a receive signal. Theelectronic device also includes means for isolating the transmittingmeans from the receive signal and for isolating the receiving means fromthe transmission signal, the isolating means coupled to a first signalpath and a second signal path. The electronic device also includes meansfor shifting a phase of a first portion of the transmission signal onthe first signal path to correlate to a phase of a second portion of thetransmission signal on the second signal path. The electronic devicealso includes means for combining the first portion of the transmissionsignal on the first signal path and the second portion of thetransmission signal on the second signal path into a combined signal.The electronic device also includes antenna means.

Various refinements of the features noted above may exist in relation tovarious aspects of the present disclosure. Further features may also beincorporated in these various aspects as well. These refinements andadditional features may exist individually or in any combination. Forinstance, various features discussed below in relation to one or more ofthe illustrated embodiments may be incorporated into any of theabove-described aspects of the present disclosure alone or in anycombination. The brief summary presented above is intended only tofamiliarize the reader with certain aspects and contexts of embodimentsof the present disclosure without limitation to the claimed subjectmatter.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawingsdescribed below.

FIG. 1 is a block diagram of an electronic device, according to anembodiment of the present disclosure.

FIG. 2 is a perspective view of a notebook computer representing anembodiment of the electronic device of FIG. 1.

FIG. 3 is a front view of a handheld device representing anotherembodiment of the electronic device of FIG. 1.

FIG. 4 is a front view of another handheld device representing anotherembodiment of the electronic device of FIG. 1.

FIG. 5 is a front view of a desktop computer representing anotherembodiment of the electronic device of FIG. 1.

FIG. 6 is a perspective view of a wearable electronic devicerepresenting another embodiment of the electronic device of FIG. 1.

FIG. 7 is a schematic diagram of an example transceiver circuitry of theelectronic device of FIG. 1, according to an embodiment of the presentdisclosure.

FIG. 8A is a schematic diagram of a receiver circuit of the exampletransceiver circuitry of FIG. 7, according to an embodiment of thepresent disclosure.

FIG. 8B is a schematic diagram of a transmitter circuit of the exampletransceiver circuitry of FIG. 7, according to an embodiment of thepresent disclosure.

FIG. 9 is a schematic diagram of the example transceiver circuitry ofFIG. 7 with a combiner circuit and antenna tracker, according to anembodiment of the present disclosure.

FIG. 10 is a schematic diagram of an example transceiver circuitry ofthe electronic device of FIG. 1 illustrating a path of a transmission(TX) signal, according to an embodiment of the present disclosure.

FIG. 11 is a schematic diagram of an example transceiver circuitry ofthe electronic device of FIG. 1 illustrating a path of a received (RX)signal, according to an embodiment of the present disclosure.

FIG. 12 is a schematic diagram of an example transceiver circuitry ofthe electronic device of FIG. 1 with baluns in the isolation circuit andthe combiner circuit, according to an embodiment of the presentdisclosure.

FIG. 13 is a schematic diagram of an transceiver circuitry of theelectronic device of FIG. 1 with capacitors in the isolation circuit andthe combiner circuit, according to an embodiment of the presentdisclosure.

FIG. 14 is a schematic diagram of an example transceiver circuitry ofthe electronic device of FIG. 1 with example circuitry for baluns, aphase shifter, and an antenna tracker, according to an embodiment of thepresent disclosure.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments will be described below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be appreciated that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features. Use of the term“approximately,” “near,” “about”, and/or “substantially” should beunderstood to mean including close to a target (e.g., design, value,amount), such as within a margin of any suitable or contemplatable error(e.g., within 0.1% of a target, within 1% of a target, within 5% of atarget, within 10% of a target, within 25% of a target, and so on).

With the foregoing in mind, there are many suitable communicationdevices that may include and use the transceiver circuitry describedherein. Turning first to FIG. 1, an electronic device 10 according to anembodiment of the present disclosure may include, among other things, aprocessor core complex 12 including one or more processor(s), memory 14,nonvolatile storage 16, a display 18, input structures 22, aninput/output (I/O) interface 24, a network interface 26, and a powersource 29. The various functional blocks shown in FIG. 1 may includehardware elements (including circuitry), software elements (includingcomputer code stored on a computer-readable medium) or a combination ofboth hardware and software elements. It should be noted that FIG. 1 ismerely one example of a particular implementation and is intended toillustrate the types of components that may be present in electronicdevice 10.

By way of example, the electronic device 10 may represent a blockdiagram of the notebook computer depicted in FIG. 2, the handheld devicedepicted in FIG. 3, the handheld device depicted in FIG. 4, the desktopcomputer depicted in FIG. 5, the wearable electronic device depicted inFIG. 6, or similar devices. It should be noted that the processor(s) 12and other related items in FIG. 1 may be generally referred to herein as“data processing circuitry.” Such data processing circuitry may beembodied wholly or in part as software, software, hardware, or anycombination thereof. Furthermore, the processor(s) 12 and other relateditems in FIG. 1 may be a single contained processing module or may beincorporated wholly or partially within any of the other elements withinthe electronic device 10.

In the electronic device 10 of FIG. 1, the processor(s) 12 may beoperably coupled with a memory 14 and a nonvolatile storage 16 toperform various algorithms. Such programs or instructions executed bythe processor(s) 12 may be stored in any suitable article of manufacturethat includes one or more tangible, computer-readable media. Thetangible, computer-readable media may include the memory 14 and/or thenonvolatile storage 16, individually or collectively, to store theinstructions or routines. The memory 14 and the nonvolatile storage 16may include any suitable articles of manufacture for storing data andexecutable instructions, such as random-access memory, read-only memory,rewritable flash memory, hard drives, and optical discs. In addition,programs (e.g., an operating system) encoded on such a computer programproduct may also include instructions that may be executed by theprocessor(s) 12 to enable the electronic device 10 to provide variousfunctionalities.

In certain embodiments, the display 18 may be a liquid crystal display(LCD), which may facilitate users to view images generated on theelectronic device 10. In some embodiments, the display 18 may include atouch screen, which may facilitate user interaction with a userinterface of the electronic device 10. Furthermore, it should beappreciated that, in some embodiments, the display 18 may include one ormore light-emitting diode (LED) displays, organic light-emitting diode(OLED) displays, active-matrix organic light-emitting diode (AMOLED)displays, or some combination of these and/or other displaytechnologies.

The input structures 22 of the electronic device 10 may enable a user tointeract with the electronic device 10 (e.g., pressing a button toincrease or decrease a volume level). The I/O interface 24 may enableelectronic device 10 to interface with various other electronic devices,as may the network interface 26. The network interface 26 may include,for example, one or more interfaces for a personal area network (PAN),such as a BLUETOOTH® network, for a local area network (LAN) or wirelesslocal area network (WLAN), such as an 802.11x WI-FI® network, and/or fora wide area network (WAN), such as a 3^(rd) generation (3G) cellularnetwork, universal mobile telecommunication system (UMTS), 4^(th)generation (4G) cellular network, long term evolution (LTE®) cellularnetwork, long term evolution license assisted access (LTE-LAA) cellularnetwork, 5^(th) generation (5G) cellular network, and/or New Radio (NR)cellular network. In particular, the network interface 26 may include,for example, one or more interfaces for using a Release-15 cellularcommunication standard of the 5G specifications that include themillimeter wave (mmWave) frequency range (e.g., 24.25-300 gigahertz(GHz)). The network interface 26 of the electronic device 10 may allowcommunication over the aforementioned networks (e.g., 5G, Wi-Fi,LTE-LAA, and so forth).

The network interface 26 may also include one or more interfaces for,for example, broadband fixed wireless access networks (e.g., WIMAX®),mobile broadband Wireless networks (mobile WIMAX®), asynchronous digitalsubscriber lines (e.g., ADSL, VDSL), digital videobroadcasting-terrestrial (DVB-T®) network and its extension DVB Handheld(DVB-H®) network, ultra-wideband (UWB) network, alternating current (AC)power lines, and so forth.

As illustrated, the network interface 26 may include a transceiver 30.In some embodiments, all or portions of the transceiver 30 may bedisposed within the processor core complex 12. The transceiver 30 maysupport transmission and receipt of various wireless signals via anantenna (not shown in FIG. 1). An impedance of the antenna may disturbthe duplex function and degrade isolation between the transmit path andthe receive path. To prevent such disruption by the antenna, an antennatracker may be used to substantially match an impedance of the antenna.

In some embodiments, the transceiver 30 may include a duplexer (notshown in FIG. 1). A duplexer enables bidirectional communication over asingle path while separating signals traveling in each direction fromone another. For example, the duplexer may isolate a transmitter of theelectronic device 10 from a received signal and/or isolate a receiver ofthe electronic device 10 from a transmission signal (e.g., isolate thetransmitter from the receiver, and vice versa). In some embodiments, theduplexer may include a balance-unbalance transformer (e.g., a balun)that isolates the transmitter from a received signal and/or isolates thereceiver from a transmission signal.

In some embodiments, the electronic device 10 communicates over variouswireless networks (e.g., WIMAX®, mobile WIMAX®, 4G, LTE®, 5G, and soforth) using the transceiver 30. The transceiver 30 may transmit andreceive RF signals to support voice and/or data communication inwireless applications such as, for example, PAN networks (e.g.,BLUETOOTH®), WLAN networks (e.g., 802.11x WI-FI®), WAN networks (e.g.,3G, 4G, 5G, NR, and LTE® and LTE-LAA cellular networks), WIMAX®networks, mobile WIMAX® networks, ADSL and VDSL networks, DVB-T® andDVB-H® networks, UWB networks, and so forth. The power source 29 of theelectronic device 10 may include any suitable source of power, such as arechargeable lithium polymer (Li-poly) battery and/or an alternatingcurrent (AC) power converter.

In certain embodiments, the electronic device 10 may take the form of acomputer, a portable electronic device, a wearable electronic device, orother type of electronic device. Such computers may be generallyportable (such as laptop, notebook, and tablet computers), or generallyused in one place (such as conventional desktop computers, workstations,and/or servers). In certain embodiments, the electronic device 10 in theform of a computer may be a model of a MacBook®, MacBook® Pro, MacBookAir®, iMac®, Mac® mini, or Mac Pro® available from Apple Inc. ofCupertino, Calif. By way of example, the electronic device 10, takingthe form of a notebook computer 10A, is illustrated in FIG. 2 inaccordance with one embodiment of the present disclosure. The depictednotebook computer 10A may include a housing or enclosure 36, a display18, input structures 22, and ports of an I/O interface 24. In oneembodiment, the input structures 22 (such as a keyboard and/or touchpad)may be used to interact with the computer 10A, such as to start,control, or operate a graphical user interface (GUI) and/or applicationsrunning on computer 10A. For example, a keyboard and/or touchpad mayallow a user to navigate a user interface and/or application interfacedisplayed on display 18.

FIG. 3 depicts a front view of a handheld device 10B, which representsone embodiment of the electronic device 10. The handheld device 10B mayrepresent, for example, a portable phone, a media player, a personaldata organizer, a handheld game platform, or any combination of suchdevices. By way of example, the handheld device 10B may be a model of aniPod® or iPhone® available from Apple Inc. of Cupertino, Calif. Thehandheld device 10B may include an enclosure 36 to protect interiorcomponents from physical damage and/or to shield them fromelectromagnetic interference. The enclosure 36 may surround the display18. The I/O interfaces 24 may open through the enclosure 36 and mayinclude, for example, an I/O port for a hardwired connection forcharging and/or content manipulation using a standard connector andprotocol, such as the Lightning connector provided by Apple Inc. ofCupertino, Calif., a universal serial bus (USB), or other similarconnector and protocol.

The input structures 22, in combination with the display 18, may allow auser to control the handheld device 10B. For example, the inputstructures 22 may activate or deactivate the handheld device 10B,navigate the user interface to a home screen, a user-configurableapplication screen, and/or activate a voice-recognition feature of thehandheld device 10B. Other input structures 22 may provide volumecontrol, or may toggle between vibrate and ring modes. The inputstructures 22 may also include a microphone that may obtain a user'svoice for various voice-related features, and a speaker that may enableaudio playback and/or certain phone capabilities. The input structures22 may also include a headphone input that may provide a connection toexternal speakers and/or headphones.

FIG. 4 depicts a front view of another handheld device 10C, whichrepresents another embodiment of the electronic device 10. The handhelddevice 10C may represent, for example, a tablet computer, or one ofvarious portable computing devices. By way of example, the handhelddevice 10C may be a tablet-sized embodiment of the electronic device 10,which may be, for example, a model of an iPad® available from Apple Inc.of Cupertino, Calif.

Turning to FIG. 5, a computer 10D may represent another embodiment ofthe electronic device 10 of FIG. 1. The computer 10D may be anycomputer, such as a desktop computer, a server, or a notebook computer,but may also be a standalone media player or video gaming machine. Byway of example, the computer 10D may be an iMac®, a MacBook®, or anothersimilar device by Apple Inc. of Cupertino, Calif. It should be notedthat the computer 10D may also represent a personal computer (PC) byanother manufacturer. A similar enclosure 36 may be provided to protectand enclose internal components of the computer 10D, such as the display18. In certain embodiments, a user of the computer 10D may interact withthe computer 10D using various peripheral input structures 22, such asthe keyboard 22A or mouse 22B (e.g., input structures 22), which mayconnect to the computer 10D.

Similarly, FIG. 6 depicts a wearable electronic device 10E representinganother embodiment of the electronic device 10 of FIG. 1 that mayoperate using the techniques described herein. By way of example, thewearable electronic device 10E, which may include a wristband 43, may bean Apple Watch® by Apple Inc. of Cupertino, Calif. However, in otherembodiments, the wearable electronic device 10E may include any wearableelectronic device such as, for example, a wearable exercise monitoringdevice (e.g., pedometer, accelerometer, heart rate monitor), or otherdevice by another manufacturer. The display 18 of the wearableelectronic device 10E may include a touch screen display 18 (e.g., LCD,LED display, OLED display, active-matrix organic light emitting diode(AMOLED) display, and so forth), as well as input structures 22, whichmay allow users to interact with a user interface of the wearableelectronic device 10E.

As mentioned above, the transceiver 30 of the electronic device 10 mayinclude a transmitter and a receiver that are coupled to an antenna toenable the electronic device 10 to transmit and receive wirelesssignals. Certain electronic devices may include isolation circuityhaving an electrical balanced duplexer (EBD) that isolates thetransmitter from received signals, and the receiver from transmissionsignals, thus reducing interference when communicating. In suchelectronic devices, an impedance tuner may be used to match theimpedance of the antenna to increase effectiveness of this isolation.However, the transmission path for transmission signals sent from thetransmitter may branch between the antenna and the impedance tuner. As aresult, some of the power used to transmit a transmission signal throughthe antenna may be lost when the transmission signal branches to theimpedance tuner. Similarly, the reception path for received signalsreceived from the antenna may branch between the receiver and theimpedance tuner. As a result, some of the power in the received signalreceived at the receiver may be lost (e.g., insertion loss) when thereceived signal branches to the impedance tuner.

Embodiments herein provide various apparatuses and techniques to reduceinsertion loss while maintaining isolation of the transmitter andreceiver of the electronic device 10. To do so, the embodimentsdisclosed herein include two circuit paths between an antenna and anisolation circuit. The two circuit paths may be combined, such that thepower divided between the two paths may be combined together, thusreducing insertion loss by recovering power that may have been lost dueto the circuit paths branching (e.g., from the antenna or the isolationcircuit).

With the foregoing in mind, FIG. 7 is a schematic diagram of an exampletransceiver circuitry 50 of the electronic device 10, according to anembodiment of the present disclosure. In some embodiments, the exampletransceiver circuitry 50 may be disposed in the transceiver 30 discussedwith respect to FIG. 1. In other embodiments, the transceiver circuitry50 may be disposed in the network interface and coupled to thetransceiver 30. As illustrated, the transceiver circuitry 50 includes anisolation circuit 56 disposed between a transmit (TX) circuit 52 and areceive (RX) circuit 54. The isolation circuit 56 is coupled to the TXcircuit 52 and is coupled to the RX circuit 54. The isolation circuit 56enables frequency division duplexing (FDD) by allowing signals (e.g.,transmission signals) of a first frequency range to pass through to theTX circuit 52 (e.g., via a transformer effect) and blocks signals of asecond frequency range from passing through to the RX circuit 54, whileenabling signals (e.g., received signals) of the second frequency rangeto pass through to the RX circuit 54 (e.g., via circuit paths) andblocks signals of the second frequency range from passing through to theTX circuit 52. Each frequency range may be of any suitable bandwidth,such as between 1 and 100 gigahertz (GHz) (e.g., 10 megahertz (MHz)),and include any suitable frequencies. For example, the first frequencyrange (e.g., the TX frequency range) may be between 880 and 890 MHz, andthe second frequency range (e.g., the RX frequency range) may be between925 and 936 MHz.

A first path 62 and a second path 64 each couple the isolation circuit56 to an antenna 60 via a node 69. The first path 62 and the second path64 may be bidirectional paths along which a signal to be transmitted(e.g., a TX signal) splits and travels from the TX circuit 52 to theantenna 60. Similarly, a signal received via the antenna 60 (e.g., an RXsignal) may split and travel along the first path 62 and the second path64 to the RX circuit 54.

In some embodiments, a signal from the TX circuit 52 (e.g., the TXsignal) may be divided by the isolation circuit 56. In that case, afirst portion of the TX signal may propagate along the first path 62 anda second portion of the TX signal may propagate along the second path64. The first portion of the signal and the second portion of the signalmay be combined at the node 69. Similarly, a signal received via theantenna 60 may be split into a first portion of the RX signal and asecond portion of the RX signal. The first portion of the RX signal maypropagate along the first path 62 and the second portion of the RXsignal may propagate along the second path 64. The first and secondportions of the RX signal may be combined at the isolation circuit 56and provided to the RX circuit 54. Splitting the TX signal at theisolation circuit from the TX circuit 52 or the RX signal at the node 69from the antenna 60, without combining the split signals back together,may cause an insertion loss equal to about half of a power of the TXsignal output from the TX circuit 52 or about half of a power of the RXsignal output from the antenna 60, respectively. In some embodiments,the insertion loss is about 3 decibels (dB).

In some embodiments, the isolation circuit 56 may include a balun (e.g.,a transformer balun) that enables signals (e.g., transmission signals)of a first frequency range to pass through to the TX circuit 52 (e.g.,via a transformer effect) and blocks signals of a second frequency rangefrom passing through to the RX circuit 54, while enabling signals (e.g.,received signals) of the second frequency range to pass through to theRX circuit 54 (e.g., via circuit paths) and blocks signals of the secondfrequency range from passing through to the TX circuit 52. Inparticular, the balun of the isolation circuit 56 may receive a TXsignal from the TX circuit 52, and output a first split TX signal on thefirst path 62 and a second split TX signal on the second path 64, wherethe first and second split TX signals are out of phase with one another(e.g., by approximately 180 degrees) and each have half the power of theoriginal TX signal. Previously, the first split TX signal may have beensent to the antenna 60 for transmission, while the second split TXsignal may have traveled to an impedance tuner, where the power from thesecond split TX signal may have been lost (e.g., resulting in insertionloss). Similarly, the antenna of the electronic device may have receivedan RX signal from the antenna 60, and split the RX signal into first andsecond split RX signals, where the first RX split signal may have beensent to the RX circuit 54 for processing, while the second split RXsignal may have traveled to the impedance tuner, where the power fromthe second split RX signal may have been lost (e.g., again resulting ininsertion loss).

Accordingly, the disclosed embodiments include one or more phaseshifters 58 that may be disposed along the first path 62 and/or thesecond path 64. The one or more phase shifters 58 may shift a phase of asignal along a respective path 62, 64 to substantially correlate ormatch a phase of a signal along the other path 62, 64. As illustrated, aphase shifter 58 is disposed on the first path 62. Thus, the phaseshifter 58 may shift a phase of a portion of the TX signal along thefirst path 62. In some embodiments, the phase shifter 58 or anadditional phase shifter may be disposed on the second path 64. Becausethe phase of the first portion of the TX signal on the first path 62 maybe about 180 degrees out of phase compared to the second portion of theTX signal on the second path 64, the phase shifter 58 may shift a phaseof the first portion of the TX signal on the first path 62 by about 180degrees. After the phase of the first portion of the TX signal isshifter by the phase shifter 58, the phase-shifted first portion and thesecond portion of the TX signal are substantially in-phase with eachother.

It should be understood that any combination of shifting of the twoportions of the TX signal on the first path 62 and the second path 64may be used to place the two portions of the TX signal in-phase with oneanother. For example, the phase shifter 58 may shift the phase of thefirst portion of the TX signal by about +90 degrees, and a second phaseshifter disposed on the second path 64 (not shown in FIG. 7) may shift aphase of the second portion of the TX signal by about −90 degrees.

Because the RX signal received at the antenna 60 may be split at thenode 69 without causing a phase difference between a first portion ofthe RX signal traveling along the first path 62 and a second portion ofthe RX signal traveling along the second path 64, the phase shifter 58may not shift a phase of an RX signal from the antenna to the isolationcircuit 56 along the first path 62. As illustrated, the node 69 is inthe form of a “T-line” junction (e.g., three circuit paths joinedtogether at the node 69). In additional or alternative embodiments, thenode 69 may include a combiner circuit or device as discussed in FIG. 9below, such as a Wilkinson power divider, a capacitor, or the like. Assuch, the phase shifter 58 may be deactivated for RX signals, and thusbe a unidirectional phase shifter. In other embodiments, the node 69 maycause a phase difference (e.g., approximately a 180 degree phasedifference) between the first portion of the RX signal traveling alongthe first path 62 and the second portion of the RX signal travelingalong the second path 64, and, as such, the phase shifter 58 may bebidirectional and shift a phase of the first portion of the RX signaltraveling along the first path 62 and/or the second portion of the RXsignal traveling along the second path 64 to ensure that the portions ofthe RX signal are in phase, as discussed in with respect to FIG. 9. Insuch cases, the node 69 may include, for example, a balun, which maycause the phase difference between the two portions of the RX signal.

Advantageously, shifting a phase of the first portion of the TX signalon the first path 62 enables that signal to be combined with a secondportion of the TX signal on the second path 64. Thus, the two signalsalong the respective paths 62, 64 can be constructively combined at thenode 69 prior to propagate to the antenna 60, thus recovering power lostin the TX signal due to splitting from the isolation circuit 56. Thus,insertion loss caused by splitting the TX signal at the isolationcircuit 56 may be reduced by combining the circuit paths 62, 64 andusing the transceiver circuitry 50.

Similarly, the first portion of an RX signal on the first path 62 may becombined with the second portion of the RX signal on the second path 64at the isolation circuit 56. The RX signal received at the antenna 60may be in single-ended mode. Thus, the first portion of the RX signal onthe first path 62 is in-phase with the second portion of the RX signalon the second path 64. In that case, the first and second portion RXsignal need not be phase shifted. The isolation circuit 56 combines thefirst and second portion of the RX signal, thereby recovering power lostdue to splitting the RX signal, thus reducing insertion loss.

FIG. 8A is a schematic diagram of the receive circuit (e.g., the RXcircuit) 54, according to an embodiment of the present disclosure. Asillustrated, the RX circuit 54 may include, for example, a low noiseamplifier (LNA) 80, filter circuitry 81, a demodulator 82, and ananalog-to-digital converter (ADC) 83. One or more signals received bythe antenna 60 may be sent to the RX circuit 54 via the isolationcircuit 56. In some embodiments, the RX circuit 54 may includecomponents in addition to or alternative to the LNA 80, filter circuitry81, the demodulator 82, and the ADC, 83, such as a mixer, a digital downconverter, and the like.

The LNA 80 and filter circuitry 81 may receive the combined RX signal(e.g., the first and the second portions of the RX signal) received bythe antenna 60 and combined by the isolation circuit 56. The LNA 80 mayamplify the combined RX signal to a suitable level for the rest of thecircuitry to process.

The filter circuitry 81 may include one or more types of filters such asbandpass filter, a low pass filter, or a decimation filter, or anycombination thereof. The filter circuitry 81 may remove undesired noisefrom the RX signal, such as cross-channel interference. The filtercircuitry 81 may also remove additional signals received by the antenna60 which are at frequencies other than the desired signal.

The filtered RX signal is sent to the demodulator 82. The demodulator 82may remove the RF envelope and extract a demodulated signal from thefiltered RX signal for processing. The ADC 83 receives the demodulatedanalog signal and converts the signal to a digital signal so that it canbe further processed by the electronic device 10. FIG. 8B is a schematicdiagram of the transmission circuit (e.g., the TX circuit) 52, accordingto an embodiment of the present disclosure. As illustrated, the TXcircuit 52 may include, for example, filter circuitry 85, a poweramplifier (PA) 86, a modulator 87, and a digital-to-analog converter(DAC) 88. In some embodiments, the TX circuit 52 may include componentsin addition to or alternative to the filter circuitry 85, the PA 86, themodulator 87, and the DAC 88 such as a digital up converter, etc.

A digital signal containing information to be transmitted via theantenna 60 is provided to the DAC 88. The DAC 88 converts the digitalsignal from the transmitter 89 to an analog signal. The modulator 87 maycombine the converted analog signal with a carrier signal to generate aradio wave.

The PA 86 receives signal the modulated signal from the modulator 87.The PA 86 amplifies the modulated signal to a suitable level to drivetransmission of the signal via the antenna 60. Similar to the filtercircuitry 81, the filter circuitry 85 of the TX circuit 52 may removeundesirable noise from the amplified signal to be transmitted via theantenna 60. In some embodiments, a PA, such as the PA 86, may bedisposed within the transmitter in addition to or alternative to the PA86 in the TX circuit 52. FIG. 9 is a schematic diagram of an exampletransceiver circuitry 70 of the electronic device 10 with a combinercircuit 72 and an antenna tracker 74, according to an embodiment of thepresent disclosure. The transceiver circuitry 70 includes a first phaseshifter 58 on the first path 62 and a second phase shifter 76 on thesecond path 64. The combiner circuit 72 is coupled to the first path 62,the second path 64, and the antenna 60. That is, the combiner circuit 72takes the place of the node 69 discussed with respect to FIG. 7. Theantenna tracker 74 is coupled to the combiner circuit 72 opposite theantenna 60.

The first phase shifter 58 and the second phase shifter 76 areconfigured such that the signals output from each of the phase shifters58, 76 are in-phase. In some embodiments, the phase shift of the firstphase shifter 58 may be opposite the phase shift of the second phaseshifter 76. In that case, for example, if the first phase shifter 58provides a phase shift of +90 degrees, the second phase shifter 76 mayprovide a phase shift of −90 degrees. Similarly, if the first phaseshifter 58 provides a phase shift of +10 degrees, the second phaseshifter 76 may provide a phase shift of −10 degrees. However, duringoperation, the actual phase shift of the phase shifters 58, 72 may notbe opposite but are sufficient to enable the shifted signals from thephase shifters 58, 76 to be constructively combined. That is, withoutthe phase shifters 58, 76, if the signal on the first path 62 and thesignal on the second path 64 may be out-of-phase. Thus, if the signal onthe first path 62 and the signal on the second path 64 were combinedwithout placing the signals in phase, an amplitude of the combinedsignal may be reduced compared to the original signal from the TXcircuit 52 or the antenna 60. As such, an insertion loss caused by theisolation circuit 56 might be amplified without placing the signals inphase.

The combiner circuit 72 may combine the shifted signals from the phaseshifter 58, 76 and provide the combined signal to the antenna 60 to betransmitted therefrom. The combiner circuit 72 may include any RFcombiner circuit, such as a balun, a Wilkinson power divider, acapacitor, a node, a T-line junction, and the like. Depending on thetype of combiner circuit 72 used, the combiner circuit 72 may shift aphase of a portion of a signal received by the antenna 60. For example,a signal received at the antenna 60 may be split into a first portionpropagated along the first path 62 and a second portion propagated alongthe second path 64. However, the combiner circuit 72 may shift a phaseof at least one of the first portion and the second portion. Such is thecase if the combiner circuit 72 is implemented as a balun (e.g., atransformer balun). In that case, the phase shifters 58, 76 may shift aphase of at least a respective portion of the received signal such thatthe first portion of the signal is in-phase with the second portion ofthe signal at the isolation circuit 56. The first portion and the secondportion are then combined at the isolation circuit 56 and provided tothe RX circuit 54. Thus, the phase shifters 58, 76 may be bidirectionalphase shifters and shift an RX signal propagating from the antenna 60 tothe isolation circuit 56, as well as a TX signal propagating from theisolation circuit 56 to the antenna 60.

The antenna tracker 74 has an adjustable impedance to offset animbalance between an impedance of the antenna 60 and an impedance of theisolation circuit 56. That is, the antenna tracker 74 may be adjusted tooffset a change of an impedance of the antenna 60. For example, if theimpedance of the antenna 60 changes, an impedance mismatch condition mayoccur because the impedance of the antenna 60 does not match animpedance of the isolation circuit 56. An impedance mismatch may reduceeffectiveness of the isolation of the TX and RX circuits 52, 54,resulting in inferior communication quality. In that case, the impedanceof the antenna tracker 74 may be adjusted such that the impedancemismatch condition of the antenna 60 is substantially reduced. That is,the impedance of the antenna tracker 74 is adjusted to balance theimpedance of the antenna 60.

Advantageously, the phase shifters 58, 76 increase or maximize therecovered power that would have been lost due to the isolation circuit56 and/or the combiner circuit 72 by enabling the signal on the firstpath 62 to be constructively combined with the signal on the second path64. Further, the antenna tracker 74 increase or maximizes the isolationbetween the TX circuit 52 and the RX circuit 54 by offsetting animpedance mismatch between the impedance of the antenna 60 and theimpedance of the isolation circuit 56.

FIG. 10 is a schematic diagram of an example transceiver circuitry 90 ofthe electronic device 10 illustrating a path of a transmission (TX)signal, according to an embodiment of the present disclosure. Theexample transceiver circuitry 90 is substantially similar to theschematic diagram of the transceiver circuitry 50 in FIG. 7, except thatthe transceiver circuitry 90 includes a phase shifter 76 on the secondpath 64 and depicts example paths 94, 96 of a TX signal propagatingthrough the transceiver circuitry 50. Although not shown, the antennatracker 74 discussed with respect to FIG. 9 may be included in thetransceiver circuitry 90 to improve isolation between the RX circuit 54and the TX circuit 25.

As discussed above, the TX signal 92 is provided to the isolationcircuit 56 by the TX circuit 52 to be transmitted via the antenna 60. Inaddition to preventing an RX signal from entering the TX circuit 52, theisolation circuit 56 also splits the TX signal 92 into a first portion(+TX) 94 and a second portion (−TX) 96. The first portion (+TX) 94propagates along the first path 62 and the second portion (−TX) 96propagates along the second path 64.

As discussed above, a phase of the first portion (+TX) 94 may be out ofphase from the second portion (−TX) 96 due to the isolation circuit 56.Thus, the phase shifters 58, 76 shift a phase of the respective portionsof the TX signal 92 such that the first portion (+TX) 92 and the secondportion (−TX) 96 are substantially in-phase at the node 69. As discussedabove, in some embodiments, one or both phases of the first and secondportions 94, 96 may be shifted as long as the phases of the respectiveportions are substantially in-phase at the node 69. Shifting a phase ofthe one or both of the portions 94, 96 enables the portions 94, 96 to beconstructively combined at the node 69, thereby reducing orsubstantially eliminating the insertion loss caused by the isolationcircuit.

FIG. 11 is a schematic diagram of an example transceiver circuitry 100of the electronic device 10 illustrating a path of a received (RX)signal, according to an embodiment of the present disclosure. Thetransceiver circuitry 100 is substantially similar to the schematicdiagram of the transceiver circuitry 50 in FIG. 7 except that thetransceiver circuitry 90 does not include the phase shifter 58 anddepicts example paths 104, 106 of a RX signal 102 propagating throughthe transceiver circuitry 50. Although not shown, the antenna tracker 74discussed with respect to FIG. 9 may be included in the transceivercircuitry 100 to improve isolation between the RX circuit 54 and the TXcircuit 52.

As discussed above, the RX signal 102 is received via the antenna andpropagates through the transceiver circuitry 50 to the RX circuit 54.The RX signal 102 is split into a first portion 104 and a second portion106 at the node 69. The first portion 104 propagates along the firstpath 62 and the second portion 106 propagates along the second path 64.The node 69 may not cause a phase shift of either the first portion 104or the second portion 106 of the RX signal 102. Thus, the first portion104 and the second portion 106 propagate to the isolation circuit 56 andare constructively combined thereby. The combined signal is thenprovided to the RX circuit 54 via the isolation circuit 56. Theisolation circuit 56 also serves to prevent a TX signal from enteringthe RX circuit 54.

If the combiner circuit 72 (e.g., in the form of a balun), discussedwith respect to FIG. 9, was used in place of the node 69, a phase of oneor both of the first portion 104 and the second portion 106 may beshifted. In that case, a phase shifter disposed on one or both of thefirst path 62 and the second path 64 would shift a phase of a respectiveportion 104, 106 of the RX signal 102 such that the portions 104, 106 ofthe RX signal 102 would be in-phase at the isolation circuit 56. Thus,the portions 104, 106 of the RX signal 102 would then be in-phase at theisolation circuit and are constructively combined thereby. Combining thefirst portion 104 and the second portion 106 of the RX signal 102reduces and/or substantially eliminates an insertion loss caused bysplitting the RX signal, via the node 69 or the combiner circuit 72.

FIG. 12 is a schematic diagram of an example transceiver circuitry 110of the electronic device 10 with baluns 112, 114 for the isolationcircuit 56 and the combiner circuit 72, according to an embodiment ofthe present disclosure. The transceiver circuitry 110 is substantiallysimilar to the transceiver circuitry 70 discussed with respect to FIG. 9except that the transceiver circuitry 110 includes example arrangementsof the isolation circuit 56 and the combiner circuit 72.

As illustrated, the isolation circuit 56 and the combiner circuit 72include a balance-unbalance transformer (balun) 112, 114, respectively.The balun 112 receives a TX signal from the TX circuit 52. The balun 112isolates the RX circuit 54 from the TX signal based on the frequency ofthe TX signal. That is, the balun 112 cuts off the path of the TX signalto the RX circuit 54 as it prevent signals of a certain frequency range(including the TX signal) from crossing to the RX circuit 54, andinstead directs such signals to the signal paths 62, 64. Thus, the balun112 splits the TX signal into a first portion which propagates along thefirst path 62 and a second portion which propagates along the secondpath 64.

As discussed above, the balun 112 may shift a phase of one portion ofthe TX signal compared to the other portion of the TX signal. Tocompensate, the phase shifter 58 may shift a phase of the first portionof the TX signal to substantially correlate or match the phase of thesecond portion of the TX signal. Thus, the second portion of the TXsignal from the balun 112 and the shifted first portion of the TX signalfrom the phase shifter 58 can be constructively combined and provided tothe antenna 60. In this way, combining the signal paths 62, 64 and usingthe phase shifter 58 enable the transceiver circuitry 110 to reduce orsubstantially eliminate insertion loss caused by splitting the TX signalvia the balun 112.

Similarly, an RX signal received by the antenna 60 is split by the balun114. The RX signal is split into a first portion which propagates alongthe first path 62 and a second portion which propagates along the secondpath 64. The balun 114 may shift a phase of one portion of the RX signalcompared to the other portion of the RX signal. To compensate, the phaseshifter 58 may shift a phase of the first portion of the RX signal tosubstantially correlate or match the phase of the second portion of theRX signal. Thus, the second portion of the RX signal from the balun 114and the shifted first portion of the RX signal from the phase shifter 58can be constructively combined and provided to the RX circuit 54. Inthis way, combining the signal paths 62, 64 and using the phase shifter58 enables the transceiver circuitry 110 to reduce or substantiallyeliminate all insertion loss caused splitting the RX signal via thebalun 114.

As discussed above, the impedance of the antenna tracker 74 can beadjusted to offset an imbalance between an impedance of the antenna 60and an impedance of the isolation circuit 56. Advantageously, theantenna tracker 74 enables further or improved isolation of the TXcircuit 52 and the RX circuit 54 by reducing the impedance mismatchbetween the antenna 60 and the isolation circuit 56.

FIG. 13 is a schematic diagram of an example transceiver circuitry 120of the electronic device 10 with capacitors in the isolation circuit 56and the combiner circuit 72, according to an embodiment of the presentdisclosure. The transceiver circuitry 120 is substantially similar tothe transceiver circuitry 70 discussed with respect to FIG. 9 exceptthat the transceiver circuitry 120 includes example arrangements of theisolation circuit 56 and the combiner circuit 72.

As illustrated, the isolation circuit 56 and the combiner circuit 72include capacitors 122 disposed in parallel. For both the isolationcircuit 56 and the combiner circuit 72, a first capacitor 122 isdisposed on the first signal path 62 and a second capacitor 122 isdisposed on the second signal path 64. The TX circuit 52 is coupled tothe first path 62 and the second path 64 directly and the RX circuit 54is coupled to the first path 62 and the second path 64 via thecapacitors 122 of the isolation circuit 56. That is, the capacitors 122of the isolation circuit 56 are disposed between and isolate the TXcircuit 52 from an RX signal received by the antenna 60 and/or isolateRX circuit 54 from a TX signal to be transmitted. Similarly, the antennatracker 74 is coupled to the first path 62 and the second path 64directly and the antenna 60 is coupled to the first path 62 and thesecond path 64 via the capacitors 122 of the combiner circuit 72. Thus,the capacitors 122 of the combiner circuit 72 are disposed between theantenna tracker 74 from the antenna 60. The transceiver circuitry 120combines paths for the TX signal, splits the RX signal, and enablesimpedance matching via the antenna tracker 74.

Advantageously, the capacitors 122 function substantially similar to thebaluns 112, 114 discussed with respect to FIG. 12, but may besubstantially easier to implement and provide cost savings over thebaluns 112, 114. That is, the capacitors 122 along with the phaseshifter 58 and the antenna tracker 74 enable any insertion loss causedby splitting the TX and RX signals to be reduced or substantiallyeliminated while isolating the TX circuit 52 from the RX signal and/orisolating from the RX circuit 54 from the TX signal.

FIG. 14 is a schematic diagram of an example transceiver circuitry 125with example circuitry for the baluns 56, 72, the phase shifter 58, andthe antenna tracker 74, according to an embodiment of the presentdisclosure. The transceiver circuitry 125 is substantially similar tothe transceiver circuitry 70 discussed with respect to FIG. 9 exceptthat the transceiver circuitry 125 includes example circuitry for thephase shifter 58 and the antenna tracker 74.

As illustrated, the phase shifter 58 includes multiple inductors 130disposed in series with multiple variable capacitors 132 connectedbetween the inductors 130 and coupled to ground. The variable capacitors132 enable tuning of the amount of phase shift to a signal propagatingtherethrough, such that the phase of that signal on the first path 62 isshifted to substantially match the phase of the signal on the secondpath 64. As illustrated in FIG. 10, in some embodiments, the second path64 may also include the phase shifter 58, and, as such, the variablecapacitors 132 of each phase shifter 58 may shift the signals on thepaths 62, 64 to correlate or match in phase.

The antenna tracker 74 includes multiple inductors 134 disposed inseries with a variable capacitor 136 connected between the inductors 134and coupled to ground. The antenna tracker 74 also includes a resistor138 disposed in parallel with the variable capacitors 136 and coupled toground. The variable capacitors 136 of the antenna tracker 74 enable animpedance of the antenna tracker 74 to be tuned to offset an impedanceimbalance between the antenna 60 and the isolation circuit 56. That is,the variable capacitors 136 may be used to improve or maintain asuitable level of isolation between the TX circuit 52 and the RX circuit54.

The variable capacitors 132, 136 may be coupled to and controlled by acontroller (not shown). The processor 12, discussed with respect to theelectronic device 10 of FIG. 1, may instruct the controller to adjust acapacitance of the variable capacitors 132, 136 to a suitable value. Insome embodiments, the controller may include the processor 12.

The techniques presented and claimed herein are referenced and appliedto material objects and concrete examples of a practical nature thatdemonstrably improve the present technical field and, as such, are notabstract, intangible or purely theoretical. Further, if any claimsappended to the end of this specification contain one or more elementsdesignated as “means for [perform]ing [a function] . . . ” or “step for[perform]ing [a function] . . . ,” it is intended that such elements areto be interpreted under 35 U.S.C. 112(f). However, for any claimscontaining elements designated in any other manner, it is intended thatsuch elements are not to be interpreted under 35 U.S.C. 112(f).

The invention claimed is:
 1. A radio frequency transceiver comprising: atransmit circuit configured to transmit a transmission signal; a receivecircuit configured to receive a receive signal; an isolation circuitconfigured to couple to one or more antennas, the transmit circuit andthe receive circuit, the isolation circuit configured to isolate thetransmit circuit from the receive signal and to isolate the receivecircuit from the transmission signal, the isolation circuit configuredto couple to the one or more antennas via a first signal path, and theisolation circuit configured to couple to the one or more antennas via asecond signal path; and at least one phase shifter disposed on at leastone of the first signal path and the second signal path, the at leastone phase shifter configured to cause a first portion of thetransmission signal on the first signal path to be in phase with asecond portion of the transmission signal on the second signal path. 2.The radio frequency transceiver of claim 1, wherein the isolationcircuit is configured to enable the transmit circuit to transmit thetransmission signal to the one or more antennas and block the transmitcircuit from receiving the receive signal received by the one or moreantennas.
 3. The radio frequency transceiver of claim 1, wherein the atleast one phase shifter is configured to shift a phase of a first signalon the first signal path 180 degrees.
 4. The radio frequency transceiverof claim 1, wherein the at least one phase shifter includes a firstphase shifter disposed on the first signal path and a second phaseshifter disposed on the second signal path.
 5. The radio frequencytransceiver of claim 4, wherein the first phase shifter is configured toshift a phase of a first portion of the transmission signal on the firstsignal path by +90 degrees and the second phase shifter is configured toshift a phase of a second portion of the transmission signal on thesecond signal path by −90 degrees.
 6. The radio frequency transceiver ofclaim 1, further comprising a combiner circuit coupled to the firstsignal path, the second signal path, and the one or more antennas. 7.The radio frequency transceiver of claim 6, wherein the combiner circuitis configured to split a received signal into a first received signaland a second received signal, and wherein the isolation circuit isconfigured to combine the first received signal and the second receivedsignal into a combined signal.
 8. The radio frequency transceiver ofclaim 6, wherein the combiner circuit is configured to combine a firsttransmission signal from the transmit circuit on the first signal pathand a second transmission signal from the transmit circuit on the secondsignal path.
 9. The radio frequency transceiver of claim 6, wherein thecombiner circuit comprises at least one of a balun, a Wilkinson powerdivider, a T-line junction, and a node.
 10. The radio frequencytransceiver of claim 6, further comprising an antenna tracker coupled tothe combiner circuit configured to correlate an impedance of the one ormore antennas to an impedance of the isolation circuit.
 11. Anelectronic device, comprising: one or more antennas coupled to a firstsignal path and a second signal path; a balun coupled to the firstsignal path and the second signal path, the balun being configured tooutput a first portion of a signal on the first signal path that is outof phase with a second portion of the signal on the second signal path;transmitter circuitry coupled to the balun; receiver circuitry coupledto the balun; and at least one phase shifter disposed on at least one ofthe first signal path and the second signal path between the balun,wherein the at least one phase shifter is configured to cause a phase ofthe first portion of the signal to be in phase with the second portionof the signal.
 12. The electronic device of claim 11, wherein thetransmitter circuitry comprises a power amplifier and the receivercircuitry comprises a low noise amplifier.
 13. The electronic device ofclaim 11, wherein the at least one phase shifter comprises one or moreinductors in series and one or more variable capacitors in parallel. 14.The electronic device of claim 11, wherein the at least one phaseshifter includes a first phase shifter disposed on the first signal pathand a second phase shifter disposed on the second signal path.
 15. Theelectronic device of claim 14, comprising an additional balun coupled tobalun via the first signal path and the second signal path.
 16. Theelectronic device of claim 15, comprising an antenna tracker coupled tothe additional balun opposite the one or more antennas.
 17. Theelectronic device of claim 16, wherein the antenna tracker comprisesmultiple inductors disposed in series and one or more variablecapacitors coupled between the multiple inductors and coupled to ground.18. The electronic device of claim 16, wherein the antenna tracker isconfigured to correlate an impedance of the one or more antennas to animpedance of the balun.
 19. An electronic device, comprising: means fortransmitting a transmission signal; means for receiving a receivesignal; means for isolating the transmitting means from the receivesignal and for isolating the receiving means from the transmissionsignal, the isolating means coupled to a first signal path and a secondsignal path; means for shifting a phase of a first portion of thetransmission signal on the first signal path to correlate to a phase ofa second portion of the transmission signal on the second signal path;means for combining the first portion of the transmission signal on thefirst signal path and the second portion of the transmission signal onthe second signal path into a combined signal; and antenna means. 20.The electronic device of claim 19, wherein the isolating means isconfigured to split the transmission signal into the first portion andthe second portion, and wherein the combining means is configured tosplit the receive signal from the antenna means into a third portion onthe first signal path and a fourth portion on the second signal path.